🧵 [SOLVED] Why doesn’t my ASUS B250 Mining Expert / ASRock H110 Pro BTC+ detect more than 8 GPUs? Real experience with 12× RTX 5070

Reflex007 · September 14, 2025, 2:43pm

If your B250 or H110 Pro BTC+ motherboard doesn’t detect the 9th to 12th GPU (especially under HiveOS + NVIDIA), the issue is not risers, power, or the cards themselves. It’s a system address space limitation (MMIO / BAR). Here’s the full journey and how we solved it.

Initial System Configuration:

Motherboard: ASUS B250 Mining Expert
CPU: Intel i3-9100F (also tested with G3900)
RAM: 16 GB DDR4
SSD: Patriot Burst 120 GB
PSUs: 2× Silverstone Hela 2500RZ (connected via ADD2PSU with relays)
Risers: PCIe x1 to x16, version 010 Plus
GPU: 12× Palit RTX 5070 GamingPro
OS: HiveOS (latest stable release)

The Problem:

System would consistently detect only 8 GPUs.
Adding a 9th GPU: fans spin, riser powers on, but GPU is not visible in nvidia-smi or HiveOS dashboard.
Swapping GPUs, risers, power rails did not change anything.
BIOS settings already included:

Above 4G Decoding → Enabled
CSM → Disabled
PCIe speed → Gen1 (for stability)

Step-by-step Troubleshooting

1. Tested all 12 GPUs individually:

Each card worked perfectly when connected solo or in smaller groups.

2. Tested all risers and power connections:

No faulty risers or cables.

3. Tried another board (H110 Pro BTC+):

Same issue — hard limit at 8 GPUs.

4. Analyzed system address usage with HiveOS:

Command used:

lspci -v -s <PCI address>

Example result per GPU:

Memory at f0000000 [size=64M]
Memory at 2010000000 [size=256M]
Memory at 2008000000 [size=32M]

So each RTX 5070 GPU takes up around 352 MB of MMIO memory space.

→ 12 × 352 MB ≈ 4.2 GB
→ Add chipset and BIOS overhead: requires ~6 GB MMIO space

Older chipsets like B250 or H110, especially with low-end CPUs (e.g. G3900), cannot allocate this much MMIO space even if “Above 4G Decoding” is enabled.

Solution: Hardware platform upgrade

New working setup:

Motherboard: TB560-BTC PRO
CPU: Intel i7-11700K
Same SSD, PSUs, risers, and GPUs
BIOS Settings:
- Above 4G Decoding → Enabled
- Re-BAR (Resizable BAR) → Disabled
- CSM → Disabled
- PCIe Speed → Gen1

Result: All 12× RTX 5070 GPUs now recognized and stable in HiveOS.

Key Takeaways

Configuration	Working GPU Count
B250 + G3900	6–8 GPUs max
B250 + i3-9100F	7–8 GPUs
H110 Pro BTC+ + G3900	6–8 GPUs
TB560 + G5900	9–11 GPUs (varies)
TB560 + i7-11700K	12 GPUs fully supported

Tips for building a 12-GPU rig:

Use modern motherboards (B560, Z590, etc.).
Choose at least a 10th or 11th Gen Intel CPU (e.g., i5‑10400, i7‑11700F/K).
BIOS setup:
- Enable Above 4G Decoding
- Disable Re-BAR (Resizable BAR) — not needed for mining
- Disable CSM (legacy boot)
- Set all PCIe lanes to Gen1 for maximum stability

If you’re experiencing similar problems…

I hope this post saves you hours of frustration. If you’re stuck, drop your specs and I’ll try to help.
Also, search Reddit for:

“B250 not detecting 9th GPU”

Maybe this thread will pop up and help others too.

hy502010 · July 6, 2026, 5:29pm

Hi, I am building a 12 gpu rig on tz590-BTC DUO board with i5-10500t cpu and m.2 to pcie adapter.

Currently it shows a pcie out of resource warning popup every time when booting up or rebooting. But it can boot into hiveos and mine normally with 12 card after press esc to ignore that warning.

Do you know how to turn off this pcie out of resource warning? Or is there any more bios setting I should change to resolve it. I already have:
above 4g enabled
cms and re-bar disable
pcie speed set to gen 1
turned off some unused on board device

This above guide is very helpful for me, thank you so much! And I hope you can take another look at my problem and see whether there’s a solution.

Now I need to press esc on keyboard every time I turn on or restart this rig, kind of annoying.